XUE GAO AND LIANWEN JIN
School of Electronic and Information Engineering
South China University of Technology
Guangzhou, 510640 P.R. China

This paper describes a method of real-time processing of machine-printed Chinese
postage envelopes in an automated postal system. We propose a vision-based postal envelope
identification method, and a system that can be applied to rapidly moving machine-
printed Chinese postage envelopes through the postal process. Our system uses a
high-speed camera to capture images of envelopes running on a conveying device, and
then automatically recognizes the postal address and postcode on each envelope. A laser
sensor is used to trigger the camera to capture the images. Our system supports a vocabulary
of 4,590 categories of characters, including 4,516 frequently used Chinese
characters defined in the GB2312-80 standard, 62 alphanumeric characters, and 12 punctuation
marks and symbols. Supported font styles include the Song, Fang Song, Kai, and
Hei fonts, among others, at a printed font size of 7.5 points and above. The results of an
experimental trial of the system with 761 envelope images representing 25,060 characters
revealed that an envelope with an average of 32.9 characters could be processed and
recognized within 81.38 milliseconds. The character recognition rate of postal addresses
is 98.72%. Furthermore, our system also provides a method for the real-time storage of
envelope images and recognition results into a database, which can be used in subsequent
envelope querying, tracking and management. The results of an experimental trial
with real live mails in a postal center indicated that our system could achieve a speed of
21,000 envelopes per hour, with the character recognition rate of postal addresses as
high as 98.92%.

Received February 9, 2011; revised August 24, 2011; accepted August 31, 2011.
Communicated by Yuh-Jye Lee.
* This work was supported in part by NSFC (No. U0735004, 60772116, 61075021) and GDSFC (No. S201102-0000541, 2010B090400397, 2010A090100016).